Regional AAG - 2008

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  1. 1. Historical Analysis of Disturbance Zones on Finley Creek, Southwest Missouri
    Derek J. Martin a and Robert T. Pavlowskybc
    aResearch Specialist, Ozarks Environmental and Water Resources Institute, Missouri State University
    bDirector, Ozarks Environmental and Water Resources Institute, Missouri State University
    cProfessor ofphysical geography, Department of Geography, Geology and Planning, Missouri State University
    This project applies geographic information systems (GIS) and the use of historical aerial photograph analysis to quantify channel change and assess watershed- and reach-scale relationships among channel disturbance zones, riparian vegetation, bank erosion, and gravel bar distribution along Finley Creek, southwest Missouri.Historical aerial photograph coverage of the main stem of Finley Creek was acquired for the years 1955, 1979, and 2005.Channel bank lines, gravel bars, and riparian land cover were digitized from each of the georectified photographs and overlaid in a GIS in order to identify disturbance zones.Disturbance zones were organized into one of four types: (i) extension, (ii) translation, (iii) chute cutoff, or (iv) megabar.Spatial analyses were performed to examine possible controlling factors of disturbance type development and evolution such as tributary and sub-watershed inputs, valley characteristics, channel confinement, and landuse/landcover.Initial investigations suggest that tributary drainage area and land use as well as valley characteristics exert a strong influence on disturbance reach development, whereas riparian land cover appears to have a negligible effect.This finding may result from the internal forcing effect that excess gravel bar deposition has on the channel bank erosion that is independent of bank resistance offered by vegetation.
    Results and Conclusions
    Study Area
    Finley Creek Watershed Characteristics
    Mega-bar Formation
    Kansas City
    Chute Cutoff
    St. Louis
    Research Objectives
    • Identifyand classify disturbance zones on mainstem of Finley Creek
    • 2. Investigate possible controlling factors of disturbance zone/type development
    • 3. Interpret disturbance formation/evolution within the context of Ozarks physiography
    Whats a Disturbance Zone?
    Chute Cutoff
    Megabar Formation
    median mig rate of .97m/yr
    median mig rate of 2.23 m/yr
    median length of 43.0 m
    median channel displacement of 41.0m
    • An area where excessive erosion or deposition has taken place, often resulting in extreme changes in channel pattern (Jacobson, 1995)
    Disturbance Zones in Ozark Streams
    Aerial Photograph Acquisition
    3. Data Analysis
    Dist Zone Determination
    1. Historical Aerial Photograph Analysis
    Maximum RMS error of 3.0
    From Jacobson, 1995
    Dist Zone Classificaton
    Ozarks stream disturbance zone as described by Oscar H. Hershey - 1895
    Photo Acquisition
    Watershed Variables
    Aerial Photograph-Derived Data
    Photo Rectification
    Disturbance Zone Identification
    Error Analysis
    Migration Rates
    generally a narrow tract of river swamp deposit spreads to a few times the width of the stream, and changes about from side to side as it is displaced by the river approaching the bluffs
    Centerline buffer based on maximum photo rectification test point error
    Some literature suggests that channel migration (disturbance) occurs more frequentlyin areas dominated by grass as opposed to trees.However, within the Finley River, riparian landcover appears to play no role in the development of disturbance areas.There was no difference between stable and disturbance zoneswhen comparing them with the dominant landcover.
    Drainage Area
    Active Channel Width
    2. Data Extraction/Compilation
    Confinement Ratio
    Riparian Landcover Analysis
    ValleyConfinement Influence
    Valley Width
    Channel Centerlines
    Centerline Buffer for Error Compensation
    Centerline Buffer forRiparian Landcover
    Gravel Bars
    Riparian Landcover
    Channel Pattern Classification
    DEM-Derived Data
    Brice, 1975
    In order to understand the history and behavior of disturbance zones in Finley Creek , they must first be identified and classified.Disturbance zone classifications have been adapted from the following chronology of channel pattern classifications.
    Watershed Delineation
    Slope Derivation
    10m DEM
    Nanson and Hickin, 1983
    Schumm, 1981
    A t-test ( = .05) confirms that disturbance zones tend to form in areas with higher confinement ratios than stable zones.
    Although dramatic changes in channel form have taken place at many disturbance areas, sinuosity has remained relatively stable.
    Lobing and Compound Growth
    Meander Classification
    Stream Network
    Sub-watershed Delineation
    Continued Research
    Straight: 1.25
    Continued research will focus on factors affecting the development of each specific type of disturbance zone such as specificcharacteristics of valley confinement , contributing drainage area, and gravel accumulations.
    Confining Valley Features